The invention relates to a process for forming a part including a bore with a bearing integrally cast therein. The invention also relates to the resulting bearing and to a mandrel and to associated apparatus particularly adapted to produce such a bearing. Such bearings are particularly useful in track rollers utilized with heavy duty earth moving equipment.
Track rollers on track type tractors typically utilize a pair of such bearings to absorb both radial and axial loads, which in such equipment can be severe. Each bearing takes the form of an axially directed sleeve portion to which is joined a radially directed flange portion. The bearings rotatably support a track roller on a shaft such that both radial and axial loads are satisfactorily accomodated.
Some prior art bearings have taken the form of integrally cast units wherein the entire bearing includes a sleeve portion which transcends to a radial flange or thrust surface portion. These prior art bearings have not proven to be entirely satisfactory in view of the relatively high cost incidental to casting the integral thrust surface portion. Also, it has been generally necessary to heat up the part to which the bearing is to be cast after the part has been formed and quenched to a desired hardness.
One solution to this problem is the construction described in U.S. Pat. No. 3,624,881, issued Dec. 7, 1971 to Brown et al and assigned to the assignee hereof. This solution takes the form of a two piece bearing joined into a unitary whole by the process of friction welding.
A problem with a friction welding construction is engendered by the necessity of properly indexing the bearings within their supporting bushings so as to insure alignment of the oil holes in their respective elements. While this is not a problem in all cases, it is in some, and more particularly in the cases where small shafts are concerned. Another problem is that a failure to provide alignment of the oil holes between the oil reservoir containing support bushing and the bearing will tend to cut off the supply of necessary lubricant and result in damage to the bearing, bushing and shaft.
Another solution to the problem is the construction described in U.S. Pat. No. 3,795,428, issued Mar. 5, 1974 to Paine et al and assigned to the assignee hereof. This solution takes the form of a two piece interlocked support/thrust bearing. The interlocking means serves to join the pieces into a unit and also serves to prevent relative rotation between the pieces.
Problems with the two piece interlock support/thrust bearings are engendered by the care that must be taken to make them interlocking and the inherent cost in so formulating them. Also, costs of assembly are somewhat higher than desirable. Finally, under the very high weight of modern-day track roller utilizing vehicles, larger and more durable track roller bearings are desirable, as are inexpensive methods and apparatus to formulate them.
Accordingly, it is an object of the present invention to provide an inexpensive process for forming a rugged part such as a roller bearing, wherein the bearing is integrally bonded to the bore of a track roller and wherein production of the part is relatively inexpensive in that it requires only a single heating of a billet from which the part is formed.